Category Archives: Indian Ocean

Tropical Cyclone 04A Organizes in the Arabian Sea

A center of circulation organized quickly within a broader area of thunderstorms over the Arabian Sea on Wednesday and the system was designated Tropical Cyclone 04A.  At 11:00 p.m. EDT on Wednesday the center of Tropical Cyclone 04A was located at latitude 13.7°N and longitude 64.0°E which put it about 705 miles east-southeast of Salalah, Oman.  The tropical cyclone was moving toward the west-northwest at 6 m.p.h.  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were wind gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure 993 mb.

The organization of Tropical Cyclone 04A improved significantly on Wednesday.  A primary rainband wrapped almost entirely around the center of circulation and there were indications on various satellite images that an eye could be forming.  Additional rainbands were beginning to form in the circulation outside the core.  Thunderstorms near the center of circulation were generating upper level divergence, especially on the northeast side of the tropical cyclone.

The environment is favorable for further intensification.  Tropical Cyclone 04A is over water where the Sea Surface Temperature is near 28°C.  Although there are strong upper level westerly winds north of the cyclone, the upper level winds over it are relatively light.  As a result there is not a lot of vertical wind shear over Tropical Cyclone 04A.  The cyclone is likely to intensify during the next several days and it could intensify rapidly.  It could attain hurricane intensity in a day or two and it could eventually become the equivalent of a major hurricane.

A ridge north of Tropical Cyclone 04A is steering it slowly toward the west-northwest.  The ridge is expected to continue steering the cyclone toward the west during the next few days.  On its anticipated track Tropical Cyclone 04A could approach the coast of Oman and Yemen in four or five days.

Tropical Cyclone 02B Forms Near Bangladesh

An area of low pressure over the extreme northern portion of the Bay of Bengal developed enough characteristics of a tropical cyclone to be designated Tropical Cyclone 02B.  At 5:00 a.m. EDT on Wednesday the center of Tropical Cyclone 02B was located at latitude 21.3°N and longitude 91.4°E which put it about 80 miles south-southwest of Chittagong, Bangladesh.  It was moving toward the north-northeast at 4 m.p.h.  The maximum sustained wind speed was 40 m.p.h. (65 km/h) and there were gusts to 50 m.p.h. (80 km/h).  The minimum surface pressure was 1001 mb.

The circulation around Tropical Cyclone 02B slowly organized during the past several days and it now has the structure of a tropical cyclone.  There are several spiral bands of thunderstorms, although most of the thunderstorms are south of the center due to the proximity to land.  The tropical cyclone is over very warm water where the Sea Surface Temperature is near 31°C, and it has enough energy to intensify.  However, a large upper level ridge over Asia is generating moderate northeasterly winds over the circulation which is producing moderate vertical wind shear.  Proximity to land will also be an inhibiting factor.  Some modest intensification is possible before the center moves over land.

Tropical cyclone 02B is moving around the western end of a subtropical ridge which is steering it northward toward the coast of Bangladesh.  That general steering pattern is expected to continue for another 24 hours.  Then the easterly winds associated with the upper level ridge over Asia are expected to turn Tropical Cyclone 02B toward the west.  On its anticipated track Tropical Cyclone 02B could make landfall over Bangladesh in approximately 24 hours.  Given the bathymetry of the northern Bay of Bengal and the shape of the coast of Bangladesh some storm surge is possible.  Locally heavy rainfall could contribute to flooding as the tropical cyclone moves inland.

Tropical Cyclone Ashobaa Moving Slowly Toward Oman

Tropical Cyclone Ashobaa moved slowly westward toward Oman on Wednesday.  At 11:00 p.m. EDT on Wednesday the center of Tropical Cyclone Ashobaa was located at latitude 20.6°N and longitude 61.1°E which put it about 160 miles (260 km) east of Masirah Island, Oman.  Ashobaa was moving toward the west at 4 m.p.h. (6 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 992 mb.

Most of the strong thunderstorms are occurring south and west of the center Ashobaa.  An upper level ridge located over southern Asia is generating easterly winds over the top of the tropical cyclone.  Those easterly winds are producing moderate amounts of vertical wind shear and account for the asymmetric distribution of thunderstorms.  Ashobaa is moving over warm Sea Surface Temperatures and there is enough energy in the upper ocean to support intensification.  However, the vertical shear is strong enough to inhibit intensification.  Once Ashobaa moves closer to the coast of Oman, the circulation will begin to pull in drier air from land.  The tropical cyclone could start to weaken before the center moves on land.

The ridge over southern Asia strengthened on Wednesday and it pushed Ashobaa a little south of due west.  The ridge is expected to remain in place and to continue steering the tropical cyclone westward for the next several days.  On its anticipated track, Ashobaa would make landfall in Oman in about 24 to 36 hours.

Tropical Cyclone Ashobaa Moves Toward Oman

Tropical Cyclone Ashobaa turned toward the west on Tuesday and it now appears on track to make a landfall in Oman.  At 11:00 p.m. EDT on Tuesday the center of Tropical Cyclone Ashobaa was located at latitude 21.2°N and longitude 61.6°E which put it about 200 miles (325 km) east-northeast of Masirah Island, Oman.  Ashobaa was moving toward the west-northwest at 11 m.p.h. (18 km/h).  The maximum sustained wind speed was 65 m.p.h. (105 km/h) and there were gusts to 80 m.p.h. (130 km/h).  The minimum surface pressure was 985 mb.

The circulation around Tropical Cyclone Ashobaa is showing signs of greater organization.  A band of thunderstorms has wrapped around the southern portion of the center of circulation and it could represent the formation of a partial eyewall.  Ashobaa is moving over water where the Sea Surface Temperature is warm, but an upper level ridge north of the tropical cyclone is generating easterly winds.  Those winds are producing some vertical wind shear which is inhibiting intensification.  The shear decreased somewhat on Tuesday and there was a modest increase in the wind speed.  The strong thunderstorms near the center of Ashobaa are generating some upper level divergence, mainly on the western side of the circulation and the tropical cyclone could intensify further during the next 24 hours.  As the circulation nears the coast of Oman, the circulation will start to pull in drier air from land and Ashobaa will start to weaken.

An upper level ridge north Ashobaa has strengthened and it appears the ridge will steer the tropical cyclone westward to the coast of Oman.  On its anticipated track the center of Tropical Cyclone Ashobaa will approach the coast of Oman near As Suwayh in about 24 hours.

Tropical Cyclone Ashobaa Moving South of Pakistan

Tropical Cyclone Ashobaa moved northwestward across the Arabian Sea south of Pakistan on Monday.  At 11:00 p.m. EDT on Monday the center of Tropical Cyclone Ashobaa was located at latitude 20.4° and longitude 64.8°W which put it about 340 miles (550 km) south-southwest of Karachi, Pakistan.  Ashobaa was moving toward the northwest at 12 m.p.h. (19 km/h).  The maximum sustained wind speed was 50 m.p.h. (80 km/h) and there were gusts to 65 m.p.h. (105 km/h).  The minimum surface pressure was 990 mb.

More thunderstorms developed near the center of Ashobaa on Monday, but vertical wind shear is still inhibiting intensification.  Ashobaa is moving over water where the Sea Surface Temperature (SST) is warm and there is sufficient energy in the upper ocean to promote intensification.  The circulation is extracting energy from the ocean and it is generating vigorous convection west of the center of circulation.  However, an upper level ridge over southern Asia is creating moderate easterly winds over the top of Ashobaa.  The resulting vertical wind shear is the reason why the strongest storms are west of the center.  Ashobaa will spend several more days in a thermodynamic environment that favors intensification and if the upper level winds lessen, it will intensify.  Eventually, when Ashobaa gets closer to land, the circulation will start to pull in drier air, which will weaken the tropical cyclone.

A ridge over India is steering Ashobaa toward the northwest.  A trough passing north of the Arabian Sea is expected to weaken the western end of the ridge and cause the tropical cyclone to turn more toward the north for a time.  Eventually, most models are forecasting that the ridge will rebuild and steer Ashobaa toward the west-northwest.   However, some models are still predicting that Ashobaa could move northward and make landfall on the northern coast of the Arabian Sea.  The spread in the guidance from the models makes the long-term track more uncertain.

Tropical Cyclone 01A Forms Over the Arabian Sea

A low level circulation formed within a larger area of thunderstorms over the Arabian Sea and the system was classified as Tropical Cyclone 01A.  At 11:00 p.m. EDT on Sunday the center of Tropical Cyclone 01A was located at latitude 18.0°N and longitude 67.5°E which put it about 490 miles (790 km) south of Karachi, Pakistan.  It was moving toward the north-northwest at 10 m.p.h. (17 km/h).  The maximum sustained wind speed was 45 m.p.h. (70 km/h) and there were gusts to 60 m.p.h. (75 km/h).  The minimum surface pressure was 994 mb.

Tropical Cyclone 01A is over warm Sea Surface Temperatures and there is sufficient energy in the upper ocean to support further intensification.  An upper level ridge over India is creating some easterly wind over the cyclone.  The strongest thunderstorms are occurring in the western half of the core of the cyclone.  The shear will inhibit intensification, but Tropical Cyclone 01A is likely to intensify during the next day or two.  Uncertainty about the future track of the cyclone also creates uncertainty about the longer term intensity forecast.

Tropical Cyclone 01A is moving northward around the western end of the ridge over India.  A trough farther to the north over Asia is expected to weaken the ridge and at that point the steering pattern will weaken.  Model guidance is inconsistent about the future track of the cyclone.  Some models forecast that Tropical Cyclone 01A will continue to move northward into Pakistan.  Other models predict that the cyclone could curve westward before it reaches Pakistan.  Thus, there is a high degree of uncertainty about the future track of Tropical Cyclone 01A.

Tropical Cyclone Quang Nearing the Coast of Western Australia

Tropical Cyclone Quang is weakening as it nears the coast of Western Australia.  At 11:00 p.m. EDT on Thursday the center of Tropical Cyclone Quang was located at latitude 20.5°S and longitude 112.1°E which put it about 160 miles northwest of Exmouth and about 210 miles north-northwest of Coral Bay, Australia.  Quang was moving toward the southeast at 14 m.p.h.  The maximum sustained wind speed was 100 m.p.h. and there were gusts to 120 m.p.h.  The minimum surface pressure was 969 mb.

An upper level ridge northeast of Tropical Cyclone Quang is generating strong northwesterly winds and vertical wind shear over it.  The wind shear in combination with cooler Sea Surface Temperatures is causing Quang to weaken.  The wind shear and rate of weakening could increase as the tropical cyclone moves farther south.

The upper level ridge is also steering Quang toward the southeast.  On the projected track Quang would make landfall on the coast of Western Australia between Exmouth and Cape Cuvier in about 12 hours.  The forecast weakening means that Quang is likely to be the equivalent of a tropical storm when it makes landfall.  It will bring some wind and locally heavy rain to parts of Western Australia as it moves inland.

 

Tropical Cyclone Quang Intensified Rapidly Into Equivalent of a Major Hurricane

Tropical Cyclone Quang intensified very rapidly on Wednesday and it reached an intensity equivalent to a major hurricane.  At 10:00 p.m. EDT on Wednesday the center of Tropical Cyclone Quang was located at latitude 17.0°S and longitude 109.2°E which put it about 460 miles northwest of Exmouth and about 610 miles north-northwest of Carnarvon, Australia.  Quang was moving south-southeast at 6 m.p.h.  The maximum sustained wind speed was 130 m.p.h. and there were gusts to 160 m.p.h.  The minimum surface pressure was 940 mb.

As Quang moved across very warm Sea Surface Temperatures (SSTs), the upper level winds eased enough to allow it to intensify very rapidly.  Thunderstorms around the eyewall transported mass upward and generated upper level divergence in all directions, which allowed the surface pressure to decrease quickly.  The decrease in surface pressure generated the rapid increase in wind speed.    Quang is a small tropical cyclone and small tropical cyclones can intensify and weaken more quickly than larger storms.  Quang may have peaked in intensity.  As it moves farther south it will move over cooler SSTs.  Upper level wind speeds will increase along the projected track creating more vertical wind shear.  In addition, it appears that some drier air may be entering the northwestern part of the circulation.  The combination of cooler SSTs, more wind shear and drier air is likely to weaken Quang significantly before it reaches the coast of Western Australia.

Quang is moving around the western end of a subtropical ridge.  As it moves toward higher latitudes, westerly winds are likely to steer it more toward the southeast.  Quang could be approaching the coast of Western Australia between Onslow and Denham in about 48 to 60 hours.

 

Tropical Cyclone Quang Forms Northwest of Australia

After several quiet weeks in the tropics a low level circulation developed in an area of thunderstorms northwest of Australia and the system was classified as Tropical Cyclone Quang (24S) on Tuesday.  At 10:00 p.m. EDT on Tuesday the center of Tropical Cyclone Quang was located at latitude 15.2°S and longitude 109.7°E which put it about 550 miles northwest of Exmouth, Australia.  Quang was moving toward the southwest at 6 m.p.h.  The maximum sustained wind speed was 45 m.p.h. and there were gusts to 65 m.p.h.  The minimum surface pressure was 997 mb.

Tropical Cyclone Quang developed over an area where the Sea Surface Temperatures (SSTs) are near 30°C.  A subtropical ridge to the east of Quang is generating some northeasterly winds over the circulation in the upper levels.  The resulting vertical wind shear is slowing the intensification of the circulation.  However, satellite imagery indicates that Quang is becoming more well organized.  A primary rainband has wrapped most of the way around the center of circulation and an eye may be forming.  Thunderstorms near the center of circulation are increasing the upper level outflow, especially on the southern side of Quang.  Further intensification is likely and Quang could reach hurricane intensity in 24 to 48 hours.  Eventually, when Quang moves farther south, it will move over cooler SSTs.  Vertical wind shear is also likely to increase at the same time, and Quang is likely to weaken as it approaches Western Australia.

Tropical Cyclone Quang is moving around the western end of the subtropical ridge.  As it reaches the western end of the ridge, it is likely to take a more southerly track on Wednesday.  By Thursday westerly winds are forecast to begin to steer Quang to the southeast.  On its projected track, Quang would approach the coast of Western Australia in about three days.  If it weakens as expected, Quang would bring some wind and rain when it moves across Western Australia.

Tropical Cyclone 15S Forms Over the Mozambique Channel

A low level circulation developed enough organization on the eastern side of a cluster of thunderstorms over the Mozambique Channel to be classified as a tropical cyclone on Thursday.  At 11:00 p.m. EST on Thursday the center of Tropical Cyclone 15S was located at latitude 16.6°S and longitude 42.3° which put it about 110 miles east-southeast of Mogincual, Mozambique and about 200 miles northwest of Maintirano, Madagascar.  It was moving toward the south-southeast at 5 m.p.h.  The maximum sustained wind speed was 40 m.p.h. and there were wind gusts to 50 m.p.h.  The minimum surface pressure was 996 mb.

Southeasterly winds in the upper levels are creating vertical wind shear and most of the stronger thunderstorms are on the western side of the center of circulation.  However, the tropical cyclone is over warm Sea Surface Temperatures and some intensification is possible.  If the upper level winds decrease, the more rapid intensification could occur.  A gradual intensification seems more likely over the short term.

A subtropical ridge of high pressure to the east of the tropical cyclone is steering it slowly to the south.  It is likely to move into a region of weak steering winds  between that ridge of high pressure and another ridge farther to the west.  As a result, the tropical cyclone could move slowly and erratically and even become stationary at times during the next day or two.  Eventually, a third ridge of high pressure is expected to develop to the north of the system and push it westward toward Madagascar.

The tropical cyclone could be a strong tropical storm or near hurricane intensity when it reaches Madagascar.  Some wind damage is possible, but the biggest threat appears to be from locally heavy rainfall and flooding.